Sulfuric-acid manufacture.



L. BRADLEY,

SULFURIC ACID MANUFACTURE. APPLICATION F|LEDAuG.25.`|917.

Ll@ Patented Nov. 5,1918.

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LEY, 0F EAST GE, NEW JERSEY, ASSIGNOB T0 RESE si.

0N, 0F NEWT YORK, N. Y., A CORPOTIN 0F NEW Yon.;

Specication ci Letters Patent.

Patented Nov. 5, tgi.

@riginal application med February 2e, 1917, Serial No. 150,797. Dividedand this application filed August i 25, 19t?. Serial No. ld.

To all whom it may concern.:

Be it known that l, LINN BRAnmr, a citizen of the United States,residing at East Grange, in the county of Essex and State of New Jersey,have invented certain new and useful improvements in Suluric-cidMfanufacture, of which the-following is a specication.

rEllis invention relates to the manuiae` ture of sulfuric acid andsulfuric anhydrid, the objects'of the invention being to provide animproved processl of manufacture, and an improved apparatus for use inconnection withsaid process. 4'llhe present improvements relateparticularly to the purication and treatment of pyrites burner gases, orot similar gaseous mixtures containing sulfur dioxid. According to myinvention the burner gases, while at a temperature above the point atwhich any substantial condensation of sulfuric acid can take place, aresubjected to the action of the known apparatus for electricalprecipitation. Thereby the dust, under which term l include allsuspended or) non-gaseous particles in the gas-stream, is rapidlydeposited in a substantially dry state; while the gase- "ous bodies,including practically all of the sulfuric acid (which exists as a gas atthe operating temperature) pass on with the main gas-stream, thesulfuric acid being recovered at a later operating stage. According tothe preferredembodiment of the present invention the gases thus puriliedtrom dust are subjected to partial oxidation with cooling, for examplein a Glover tower, whereby a cloud or mist ot sulfuric acid andassociated impurities is formed;

and this cloud is then removed at a lower temperature, preferably byelectrical precipitation.

l have found that the rapidity oi deposition of dust from the highlyheated burner gases by the known apparatus for electrical precipitationis such as to permit, with a proper arrangement of apparatus, apractically complete elimination of dust while avoiding such fall oftemperature ot the gas as would permit the simultaneous deposition of,sulfuric acid from the mists or clouds which -tend to form when suchgasstreams are cooled. This permits me to modify in a highlyadvantageous'manner,

sign. E

as hereinafter more fully pointed out, the

present methods ot manufacture ot sulfuric acm.,

A form of apparatus operating in accordance with my invention isillustrated in the accompanying drawings, wherein the ligure `is a sideelevation, parts being shown in section, of certain plant elementsapplicable to the manufacture of chamber acid in accordance with myinvention.

Referring to the gure, A represents a sulfur-dioxid generator or-pyrites burner vwhich may be of any' usual or approved type, and B anelectricalY precipitator hereinafter more fully described. C indicatesthe usual niter pots and D a Glover tower, both of which may be of anyvapproved derepresents a second electrical precipitator, whichisillustrated as of substantially the. same general construction andform as the precipitator B.

As illustrated by way of example, the electrical precipitator-Bcomprises aY casing 1 which may be of iron, constructed with aconverging bottom 2 for the collection and discharge of the precipitate.The collecting electrodes 3 have the form of a battery of open-ended,vertical, parallel tubes, which may be ln electrical contact with thecasing, the latter being suitably grounded as conventionally indicatedat 4. rl`he discharge electrodes are indicated as wires, rods or strips5, vertically positioned and extending axially through the tubularcollecting electrodes 3. The discharge electrodes are carried bytransverse conductors 6 which extend horizontally above the tubes 3 andare supported by insulators 7. 8 indicates any suitable tensioning meansfor exam le a weight or spreader, whereby the disc argc electrodes areheld in their axial position within the tubes. The insulators 7 aremounted in lateral extensions of the casing indicated by the numeral 9,and are therefore maintained at approximately the same temperature asthe gases traversing the precipitator. In the particular formillustrated these insulators are carried by vertical posts or otherappropriate supports 10, located outside of the casing l but extendinginto the extensions 9. In practice, the dischar electrodes are connectedto the negative po e of a source of high electrical potential, as is nowwell understood in this art, the discharge between the respectiveelectrodes serving to precipitate all suspended matters.' It will beobserved that the highly heated burner gases, with their burden of dust,p ass directly through due ll into the precipitator ligand it ischaracteristic of my invention that the temperature within theprecipitator B is maintained above the temperature at which .sulfuricacid (which is always present to a greater or lesser extent inthe burnergases) is deposited as a liquid. ln case the temperature were permittedto fall materially below this point, the sulfuric acid would collectupon the insulators 7, quickly rendering them useless for their intendedpurpose. Moreover, if mists or clouds of sulfuric acid bare permitted toform in the precipitator by condensation, such clouds are quicklyprecipitated with the dust, such precipitation resulting not only in`lossl of acid through neutralization by the iron oxid and other bases ofthe dust, but materially increasing the difficulty of' removing andhandling the precipitate, which may then assume the condition of asludge. Furthermore, the substantial absence of acid in the liquid phasepermits the employment in the construction of the Aprecipitator,including the electrodes, of such inexpensive materials as cast andwrought iron, etc. Ordinarily, the location of the precipitator inimmediate proximity to the burners will suilice to maintain the properworking temperature, which should preferably materially exceed 317 C.(the boiling-point of 98 per cent. sulfuric acid); but it will beunderstood that the precipitator or any portion thereof may if requiredbe covered with any of the usual heat-insulating materials, or itsproper workg temperature may be maintained by any suitable means.

The gases are thus substantially freed A from suspended impurities, andin case the sulfuric acid is to be preparedV in accordanceY with thewell-known chamber process, the

gases may pass directly to the niter pots. C, and thence to the usualGlover tower D and to the vsupplemental or low-temperature precipitatorE.

Although the supplemental purification of the gases for the removal ofimpurities which pass the electrical precipitator B in the gaseous phasemay be carried out in any desired manner, I prefer to accomplish this byinterposing in the path of the partially cooled and oxidized gasesescaping from the Glover tower D a second electricalprecipitator E,which may be of the same type as the precipitator B, or of any otherdesired type, but the operating temperature of which is below that atwhich sulfuric acid separates as a. cloud or mist. This supplementalprccipitator E is illustrated as having thesame general construction asthe 4precipitaton B, and like reference numerals are applied thereto,the precipitator however receiving the gases from the Glover tower atthe top through fiue l2, and delivering them rfrom its lower portionthrough iue i3 to the chamber system. inasmuch as this -precipitatoroperates at temperatures below the condensing-point of sulfuric acid itshould of course be constructed of materials which are not affected bysulfuric acid under the operating conditions; and the insulatorsshould-be protected by any appropriate means against loss of eciency dueto the deposition of acid thereon. This may beaccomplished for exampleby heating the insulators locally by means of resistance elements le, orin any other desired way.

Certain advantages which are secured through the practice of myinvention have already been mentioned. The principal adyantages may bebriey summarized as folows:-

(l) Since the temperature of the gas is 'maintained, during thedeposition of the dust, above the point at which sulfuric acid can existin the liquid phase, the insulators of the precipitator B. retain theirelciency, which would not be the case were even a film of sulfuric aciddeposited upon their surfaces.

Condensation of acid upon the -insulators l is eilectually prevented bylocating them in the interior of the precipitator, whereby they attainsubstantially the temperature of lthe gas-stream.

(2) The dust isprecipitated in a suiiicintly dry state to permit easyremoval and handling. f l

(3) The acid which would otherwise be lost through neutralization by thebasic constituents of the dust 'is saved, and is later recoveredin'comparatively clean and usable form.

1(4) Owing to the absence of sulfuric acid inthe liquid phase thecorrosion problems are leliminated so farv as the precipitator B 1sconcerned, and it becomes practicable to v use in its Iconstructionsheet iron and other inexpensive materials.

' (5) The bulk of the arsenic contained in the burner gases traversesthe precipitator without possibility of conversion to arsine (ASHS)through contact with iron in presence of aqueous acid. Thereby thesubsequent removal of arsenic by supplemenal purification is greatlysimplified. This subsequent puriflcation maybe carried out entirely inbrick-lined flues, etc., or otherwise under conditions to avoid contactof the condensed acid with iron surfaces.

(6) A high degree of heat-conservation may be attained, inasmuch as theprecipitating apparatus 1s relatively very small, as compared forexample `with a dust chamber capable of operating with any comparabledegree of eiiciency. Furthermore, the apparatus requires but fewopenings through which airmay enter to dilute and mamas cool the gas, ormoisture to condense the sulfur trioXid which is always present in theburner gases. The prccipitator moreover may readily be covered withsuitable heatinsulation.

(7) This heat conservation is especially advantageous in the applicationof the invention to thcchamber process, the heat of the gases beingconveyed in greater measure to the Glover tower, the operatingefliciency of which is thereby improved.

(8) It is found practicable, owing to the absence of dust to prepare aclean and salablc niter cake in the niter pots.

It is to be understood that my invention may be carried into effect inapparatus differing widely in construction and design from that hereinillustrated and described.

This application is adivision of my copending application Serial No.150,797, filed February 24, 1917.

I claim 1. In apparatus for the manufacture of sulfuric acid, thecombination with a sulfur'- dioxid generator, of two electricalprecipitators arranged in series in the line of the gasflow,A and meansinterposed between said precipitat-Ors for cooling and oxidizing thegases.

2. In apparatus for the manufacture of sulfuric acid, thev combinationwith a sulfurdioxid generator, of two electrical precipitat-ors arrangedin series in the line of the gasiow, and a Glover tower interposedbetween said precipitators.

3.In apparatus for the manufacture of sulfuric acid, the combinationwith a sulfnr-dioxid generator, of an electrical pretower or equivalentnitrifying device, of an electrical precipitator arranged to treat theexit gases therefrom before entering the chambers.

In the manufacture of sulfuric acid, the steps which consist inelectrically precipitating the dust from the burner gases whilemaintaining a suiiicient temperature to avoid substantial deposition ofsulfuric acid, then effecting a partial oxidation of the sulfur dioxidand cooling the gases to form a cloud or mist containing sulfuric acidand associated impurities, and removing said cloud.

6. In the manufacture of sulfuric acid, the steps which consist inelectrically precipitating the dust from the burner gases whilemaintaining a sufficient temperature to avoid substantial deposition ofsulfuric acid, then effect-ing a partial oxidation of the sulfur dioxidand cooling the gases to form a cloud or mist containing sulfuric acidand associated impurities, and electrically precipitating said cloud.

7. In the manufacture of sulfuric acid, the steps which consist inelectrically precipitating suspended particles from a burner as attemperatures respectively above and low the condensing point of sulfuricacid, and effecting a partial Ioxidation of sulfur dioxid between saidyprecipitating operations.

8. In the manufacture of sulfuric acid, the steps which consist inburning a sulfur-bearin material to produce a gas mixture contalningsulfur dioxid, effecting a partial oxidation of the sulfur dioxidcomponent of said gas mixture with formation of a mist or cloudcontainngsulfuric acid and associated impurities, and electricallyprecipitating said cloud.

In testimony whereof I alfix my signature.

LINN BRADLEY.

